Download The Night Sky - Faculty

The Night Sky
Venus Returns to the Evening Sky
As the month of December begins, evening sky only has one planet that will be easily visible, that planet
being Mars. However as the month progresses Venus will start to emerge from the bright evening
twilight. During the last week of December, bright Venus will be low in the west-southwest sky, setting
a little over an hour after the sun. For those of you with unobstructed western horizons, you might be
able to catch planet Mercury to the lower right of the much brighter Venus on the last few days of
December. As it has done for the past few months, Mars continues to race the sun on the sky and keep
pace with it, remaining at nearly the same altitude all month an hour after sunset low in the westsouthwestern sky. Mars leaves the constellation of Sagittarius and travels through Capricornus during
this last month of the year. The red planet sets approximately 3 hours after the sun all month long.
At the beginning of December, Jupiter rises in the east around 10 p.m. By the end of the month, this
bright planet rises around 8 p.m. just as Mars is setting in the west. Jupiter will be west of Regulus, the
brightest star in Leo, all month long. On moonless nights, this `king of the planets’ will be the brightest
object in the sky once it rises.
Planet Saturn returns to the morning sky, rising about an hour before the sun as the month begins. By
the end of December, this ringed planet will rise some 3 hours before the sun. All through December,
Saturn will be slowly moving towards the three stars that mark head of Scorpius.
The moon will be full on the morning of December 6th. According to folklore, the December full moon is
known as the Full Cold Moon. The day prior to this, the nearly full moon will be very close to the bright
red giant star Aldebaran in Taurus as the moon moves through the Hyades star cluster. Seeing the
moon slowly move through this star cluster with binoculars is quite interesting to watch.
The Geminid meteor shower peaks on the nights of December 13-14 and 14-15 when the moon will be
near 3rd quarter. The Geminids are unique in that they can be seen during evening hours and often
show very bright meteors called bolides. Most meteors are caused by particles in space about the size
of sand grains burning up in the Earth’s atmosphere. Meanwhile, bolides result from objects the size of
a small stone as they fall through the atmosphere.
The winter solstice occurs at 6:03 p.m. on December 21st. This marks the sun’s lowest point on the sky
in the northern hemisphere and corresponds to the fewest number daylight hours of the year. This also
marks the first day of winter in the northern hemisphere.
The free public astronomy open houses at the ETSU Powell Observatory take a hiatus over the holiday
break. They will resume on January 24, 2015. Further information about these open houses can be
found on the web at http://www.etsu.edu/cas/physics/observatory/default.aspx.
This month’s Night Sky was written by Dr. Donald G. Luttermoser, Chair of the Department of Physics
and Astronomy at ETSU. He can be reached at [email protected]. Astronomy-related information
for the public, including a link to the ETSU Powell Observatory, can be found at
http://www.etsu.edu/cas/physics/outreach/astronomy.aspx.